More protein in your breakfast or snacks won’t give you more muscle without more work – a biologist separates the science from the marketing

Growing up, my brothers were fascinated by the first “Rocky” movie. They were trying to get stronger and excel in sports, so one scene stood out almost as much as Rocky sprinting up the museum steps: Before sunrise, Rocky cracked raw eggs into a glass and drank them.

To a teenager, this raised some questions. Why raw eggs? Was this what you needed to build muscle and become stronger? Curiosity eventually won, but one gulp was enough. The drink was as nasty as it looked. The scene was as much about showing Rocky’s toughness as it was about making a protein-rich drink to become stronger.

Today, Rocky’s raw eggs have been replaced by protein shakes, bars and protein-enhanced everything. Grocery shelves are filled with protein-enriched cereal, pasta, chips, coffee, bread and even protein-fortified Pop-Tarts. When a breakfast pastry known mainly for sweetness and convenience is marketed as a protein source, it is clear that food companies are capitalizing on consumers’ growing interest in protein.

As a researcher who studies proteins essential for nerve and muscle cell function, I am accustomed to thinking about what scientific evidence actually shows. There is good science around much of the current enthusiasm for protein. But many people are already getting adequate amounts of protein in their diet.

So as someone also approaching the protein mania as a health-conscious consumer, I believe it’s also important to separate the marketing push to add protein to everything from what is really necessary for good health.

What are proteins?

Along with carbohydrates and fats, protein is one of the three macronutrients you need to eat in adequate amounts for your body to function. Carbohydrates and fats are your major sources of energy. While protein can also be used for energy, its main purpose is building and repairing the body.

Protein is necessary to build and sustain muscles. This includes the skeletal muscles that Rocky uses to sprint and box, the muscles that allow your heart to beat, the muscles that squeeze food through your stomach and intestines, and the muscles that open up your airways to breathe.

But muscle is not the only body part that needs protein. Protein is also important for the functioning of your nervous system, immune system, skin, hormones and other essential components.

So protein is not just “muscle food.” It is needed throughout your body, even though the marketing of protein-rich foods focuses on muscle.

What are amino acids?

Proteins are made of amino acids, of which there are 20 types. It’s the combination and number of amino acids, as well as the shapes of the proteins they create, that give proteins different roles in the body.

Your body obtains amino acids by digesting the proteins you eat and breaking them down into these individual building blocks. How well your body absorbs amino acids and makes them available for use is affected by many factors, including the protein source and cooking. Animal proteins are generally more digestible than plant proteins, and cooking generally enhances protein digestibility. So, while Rocky’s raw eggs provided a source of protein, scrambled eggs are easier to digest and may have been a better choice.

Of the 20 different amino acids in proteins, nine are considered essential because the human body cannot make them directly and must obtain them from food. Most protein-containing foods have the majority of these essential amino acids, but some foods are low in one or more of them. Animal-based proteins, such as eggs, dairy, fish, poultry and lean meats, are good sources of the essential amino acids. Most protein-rich plant foods, such as most beans, nuts and rice, are low in one or more essential amino acids. Soybeans are an exception, providing a complete composition of essential amino acids.

Medical professionals recommend eating a variety of protein sources, including some that are complete, to ensure you’re getting all of the essential amino acids. Eating a mixture of protein-rich plant foods can overcome deficiencies in one particular plant food.

Protein powders, often used as supplements, vary in essential amino acid content and composition. Compared to animal-based powders, plant-based powders tend to have lower levels of one or more essential amino acids and lower protein levels in total.

How much protein do you need?

There is little scientific debate that dietary protein is critical to good health. A harder calculation is how much protein you need.

A commonly cited standard is the federal recommended dietary allowance, or RDA. In January 2026, the U.S. government raised the adult RDA of dietary protein from 0.8 grams per kilogram of body weight to 1.2 to 1.6 grams per kilogram. For a 150-pound person, this almost doubles the recommendation from 54 grams to between 80 to 110 grams a day. Some experts have interpreted this update as focusing on optimizing health as opposed to ensuring adequate protein intake to avoid deficiency.

The new federal guidelines are not without controversy, however. How much protein a given person needs is a complex question that depends on individual health goals, age, sex, activity level, medical history and other factors. Consulting with a medical provider or licensed nutritionist can help individualize dietary protein targets.

Many experts agree that the average, healthy U.S. adult already consumes enough protein. While most healthy adults can tolerate moderately high protein intake, overloading on protein could create health problems, such as kidney damage and digestive issues.

Companies market high-protein diets to encourage weight loss because consuming more protein tends to increase feelings of fullness. A 2026 study identified a link between the amino acid leucine and appetite suppression through a connection between the gut and the brain.

That said, while suppressing appetite may help with weight loss, it may also reduce a person’s consumption of calories from fruits, vegetables, beans and whole grains that provide fiber, vitamins and other important nutrients.

What about protein powders and supplements?

Protein powders are a US$20 billion industry, and their popularity reflects both the idea that dietary proteins can support muscle growth and reduce muscle loss as well as how lucrative protein supplements can be.

For people with low appetites or those who have difficulty meeting dietary protein recommendations, protein-enriched foods can be a useful way to increase protein intake. This might include those taking GLP-1 weight loss medications, which can reduce appetite and make it harder to eat enough protein and other nutrients.

But while a protein shake can deliver essential amino acids, it does not provide the broader nutritional value of protein-rich foods, such as fish, beans, nuts, yogurt and soy products. Moreover, protein-fortified packaged foods may come with increased sugar, salt or saturated fats. A protein bar may be closer to a candy bar with better branding.

For these reasons, medical organizations recommend consuming well-planned combinations of protein sources from nonpackaged foods.

Building muscle takes more than just protein

Beyond bodybuilding, science has elevated society’s appreciation for the importance of dietary protein in combating muscle loss due to aging, weight loss or injury.

Some experts don’t think doubling protein intake is as important to building muscle as resistance training, a type of exercise that creates force and strain on muscles to signal the body to repair and grow more muscle. This is different from endurance training that improves aerobic capacity.

A 2021 clinical trial found that only when dietary protein was combined with heavy resistance training did older adults see improved muscle size, strength and function.

Eating more protein alone will not build muscle because the critical molecular pathways for muscle growth and strength require repeatedly placing heavy forces on the muscle. Challenging your muscles with repeated training and progressively heavier weights stimulates muscles to adapt by becoming larger and better able to produce force. The nervous system adapts too, becoming better able to activate and coordinate muscle movement.

Resistance training is also key to preventing the muscle loss that accompanies weight loss from GLP-1 medications, aging and recovering from injury. The key takeaway is that dietary protein and resistance training work together to promote muscle growth and maintain strength.

Rocky knew that drinking the eggs wasn’t enough – he still had to challenge his muscles to build muscle and strength.

Protein in everything: Science vs. sales pitch

So, is the protein craze based on real science, or is it a fad?

It’s both. The science is clear – dietary protein supports muscle maintenance, growth, injury repair and recovery, fullness and weight regulation, and healthy aging. The fad is the idea that any food with added protein is automatically better – and that you can always benefit from more protein.

Protein deserves attention. But the marketing of protein-fortified food products is not a shortcut to a quality diet that provides a complete source of amino acids from nutritious foods.